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Dentistry Biological Science > Kidney 4 > Flashcards

Kidney 4 Flashcards

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1
Q

What pH do enzymes usually work in?

A

7.35-7.45

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2
Q

Where are 2 acid intakes into the body?

A

Metabolic acid production and H+ intake.

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3
Q

What are the two organs that acid is excreted from?

A

Lungs (volatile) and kidney (non-volatile)

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4
Q

What are the 4 ways which hydrogen ions is gained into the body?

A
  1. Generation of hydrogen ions from C02.
  2. Production of non-volatile
    from the metabolism of protein and other organic molecules.
  3. Gain of hydrogen ions due to loss of bicarbonate in diarrhea or other non gastic GI fluids.
  4. Gain of hydrogen due to loss of bicarbonate in the urine.
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5
Q

What are 4 ways in which hydrogen ions are lost in the body?

A
  1. Utilisation of hydrogen ions in the metabolism of various organic anions
  2. Loss of hydrogen ions in vomitus
  3. Loss of hydrogen ions in the urine
  4. Hyperventilisation
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6
Q

Every day, how many milli moles of carbon dioxide is added to plasma?

A

20,000

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7
Q

What reaction happens between carbon dioxide and water?

A

CO2 + H20 -> carbonic acid

-> bicarbonate ions and H+

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8
Q

Loss/gain of H+?
Hyperventilating
Hypoventilating

A

Hyperventilating - net loss of hydrogen ions

Hypoventilating - net gain of hydrogen ions

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9
Q

What acids are the in the body that are non-volatile?

A

Lactic, phosphoric and sulphuric acid.

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10
Q

How many mmol of protein can be added in a high protein diet?

A

40-80mmol/day

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11
Q

What expulsion mechanism removes H+? HC03-?

Explain what occurs in each?

A

H+ in sick
HCO3- in diarrhea

If you lose bicarbonate, the reaction is not reversible so the H+ cannot be breathed out so it increases.
Vice versa with H+.

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12
Q

What is the equation for pH?

What is the normal nM of H+?

A

pH = -log(H+)

35-45nM

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13
Q

Respiratory acids?

Non-respiratory acids?

A
  • CO2 production (oxidative metabolism)

- Other acids (e.g. phosphoric acid) excreted by kidneys.

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14
Q

What numerical range is plasma acid in?

Acid production?

A

nM

mM

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15
Q

Bicarbonate system

What does an increase/decrease in H+ do to the system?

A

Increase pushes it right

Decrease pushes it left

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16
Q 
Give all the buffers in the body under these titles:
Blood:
Interstitial Fluid:
Intracellular Fluid:
Urine:
A

Blood:
Bicarbonate
Haemoglobin
Plasma proteins

Interstital fluid:
Bicarbonates
Very little protein

Intracellular fluid:
Intercellular proteins
Phosphates
A little bicarbonate

Urine:
Phosphate
Ammonia

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17
Q

What happens to the intracellular pH?

All the organelles are in acidic conditions except which one?

A

Below 7.35

Except mitochondria (pH 8)

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18
Q

Which mathematical equation is important in buffer solutions?

What does buffer effectiveness depend on?

A

Henderson Hasselbach

Depends on its concentration and pK.

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19
Q

When does pH = pK?

A

When the acid is half dissociated

20
Q

What can be used in the Henderson Hasselbach equation to replace the value for bicarbonate acid solution?
Why?

A

Partial pressure for carbon dioxide

Easier to measure

21
Q

State the normal plasma values for each of these

A

Arterial CO2 = 5.3kPa
Arterial [HCO3-] = 25nM
Venous [HC03-] = 25nM
Arterial pH = 7.4

22
Q

What are the 2 processes which are controlled by acid-base balance?

A
  1. Matching output (i.e. excretion) to input

2. Regulating the ratio of base to weak acid in buffers

23
Q

What part of the buffer do the lung and the kidney regulate?

A

Kidney deals with HCO3- concentration and lung with pC02.

24
Q

What is a big advantage of the bicarbonate buffer?

A

The addition of acid causes pCO2 to rise. This drives respiration which increases elimination of CO2 from the body.

25
Q

Why is the bicarbonate buffer very effective but only a short term measure?

Why?

A

It will eventually run out of bicarbonate.

The kidney can reabsorb bicarbonate.
The kidney can rid the body of excess H+.

26
Q

Why would the pH of the urine not be as acidic as expected?

A

Low protein diet.

27
Q

What are the 3 places that bicarbonate reabsorption occurs in the kidney?

A
  1. Proximal tubule
  2. Ascending loop of Henle
  3. Cortical collecting ducts
28
Q

What are the two types of isoforms of carbonic anhydrase on the luminal membrane and in the cytosol?

A

Luminal membrane = carbonic anhydrase 4

Cytosol = carbonic anhydrase 2

29
Q

Explain bicarbonate absorption in the kidney

A

Bicarbonate moves across the basal lateral membrane into the interstitial fluid using transporters. Once here, it can pass into plasma.

30
Q

HCO3- is —- in the kidney?

H+ is —- in the kidney?

A

Absorbed to blood

Secreted to filtrate

31
Q

Explain how H+ is secreted to the filtrate

What happens if HCO3- is present in the lumen?

A 
H+ is passed into the tubular lumen via a transporter. 
This is where it forms the filtrate.
3 transporters:
1. Na-H+ countertransporters
2. H+-ATPase pumps
3. H+-K+-ATPase pumps

H+ that is secreted will not be excreted. This is because it will combine with it and form carbon dioxide and water.

32
Q

How is H+ excreted in combination with monohydrogen phosphate?

What would unbuffered H+ do to the urine pH?
What does this result in?

A

They will combine in the tubular lumen to form H2PO4 which can be excreted.

Would lower it <5

Addition of new HC03- (bicarbonate) to plasma.

33
Q

What is an additional mechanism which adds bicarbonate to plasma?

Where does the glutamine come from and how?

A

Glutamine metabolised to ammonium ions and bicarbonate ions.

It is an amino acid which can be freely filtered. It can enter kidney cells across the tubular membrane or by the means of a glutamine exchanger on the basal lateral membrane.

34
Q

What are 3 mechanisms in the body to maintain a constant pH?

How quickly do these work?
Give some details on molecules present

A
  1. Chemical buffers
  2. Brainstem respiratory centre
  3. Renal mechanisms
  4. Seconds, bicarbonate in ECF, phosphate in ICF, phosphate or ammonia in urine
  5. Minutes, responds to changes in arterial pCO2, pO2 and [H+]. Adjust ventilation to retain or expel CO2.
  6. Hours to days, for each H+ secreted, HCO3 is added to the blood.
35
Q

What are the 4 acid-base disorders?

Which type affects carbon dioxide partial pressure? Which affects bicarbonate concentration?

A

Acidosis and Alkalosis

Either can be respiratory or metabolic.

Respiratory, metabolic

36
Q

What is bicarbonate concentration controlled by and altered by?

How about carbon dioxide partial pressure?

A

Controlled by kidney, altered by metabolic disorders

Controlled by respiration, altered by respiratory disorders.

37
Q

What happens to pH, partial pressure of carbon dioxide and concentration of bicarbonate in metabolic acidosis?

A

Decrease, no change, decrease

38
Q

What is compensation?

A

When a primary acid-base disorder exists, the body attempts to return the pH back to normal

39
Q

Give details on respiratory acidosis

  • types
  • affects
A

Increases pH, increase pCO2 conc, normal bicarbonate conc.
Caused by insufficient CO2 excretion by the lungs.
Types:
1) Acute - abrupt failure in ventilation, could be air way obstruction
2) Chronic - secondary to many disorders, long term, can lead to chest disorders

40
Q

Explain the 3 reasons in terms of respiratory acidosis

A

1) Chemical buffers (some of the retained C02 is converted to HC03- by carbonic anhydrase, this means arterial pCO2 increase so reaction goes to the right
2) Brainstem respiratory centre - adjust ventilation to expel carbon dioxide
3) Renal mechanisms - For each H+ secreted, HC03 reabsorbed. Kidney will retain bicarbonate and synthesise it from glutamine.

41
Q

Give details on metabolic acidosis and compensation

A

Types:
HC03-
Can be due to no bicarbonate reabsorption in kidney or GI problem (diaahorea).
H+ gain
Can be due to exogenous acid, abnormal lipid or carbohydrate metabolism or normal protein metabolism.

Compensation:

1) Initial increase in blood H+ will cause bicarbonate conc to fall and pCO2 to rise. Blood H+ increases so pH decreases and this leads to reduction in bicarbonate conc
2) Increase in ventilation
3) Increase in glutamine metabolism so H+ secretion increases

42
Q

Explain respiratory alkalosis and how this is compensated

A

Caused by: excessive central respiratory drive (e.g. aspirin overdose, fever, brainstem damage) or hypoxic stimulation (e.g. response to altitude, hysterical hyperventilation, pulmonary embolism).

When excess CO2 is lost from the lungs.

1) [HCO3 ̄] decreases as some of it reacts with H+ to produce CO2 so both HCO3- and H+ decrease (pH rises).
2) Reduce ventilisation
3) Kidneys respond to fall in pCO2 with reduction in H+ secretion into tubules.
There is now insufficient H+ to ensure the reabsorption of all the HCO3 ̄ in filtrate, and HCO3 ̄ is excreted in the urine, which is alkaline (pH.7.4).
The end result is pCO2 is still low, pH high and [HCO3 ̄] low, but changes smaller than they would otherwise be.

43
Q

Explain metabolic alkalosis and compensation

A

Caused by:
Repeated vomiting (loss of gastric acid)
Excess Aldosterone (stimulates H+-ATPase pump)
Excress alkali ingestion

1) There is a decrease in [H+] concentrations so pH increases. There will be an increase in plasma bicarbonate concentration so reaction goes to the left
2) pH changes will inhibit respiration, causing additional CO2 to be retained in the body. Stimulates respiration
3) Kidneys should excrete excess bicarbonate. Pendrin (bicarbonate hydeogen ecahnger) comes into play on the type B intercalated cells of colecting duct to produce more H+

44
Q

Names for these:
Reduced blood pH is associated with increased plasma potassium

Increased blood pH is associated with decreased plasma potassium

A

Hyperkalemia

Hypokalemia

45
Q

What 4 factors affect K+ secretion by principal cells of the collecting duct?

A
  1. Factors affecting Na+ entry through epithelial Na+ channels (ENaC).
  2. Aldosterone stimulates K+ channels.
  3. Tubular flow rate. High flow rates favour secretion.
  4. Acid-base balance. Acidosis inhibits it and alkalosis enhances it. Normal plasma K+ 3.5-5.0 mMX%
46
Q

What does acidosis do to K+ movement?

A

Movement of K+ depends on the electrochemical gradient. Acidosis = reduce electrochemical gradient for K+ and reduce movement as the filtrate will have a lower pH.

Dentistry Biological Science (88 decks)

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